LMWH-calibrated anti-FXa assays showed good agreement with drug-specific assays (κ = 0.76 for rivaroxaban, κ = 0.82 for apixaban) and can reliably exclude clinically relevant concentrations of these drugs.
Cross-Sectional (n=61)
No
Can a commercial LMWH-calibrated anti-FXa assay be used to exclude the presence of clinically relevant concentrations of rivaroxaban and apixaban in patients with non-valvular atrial fibrillation?
LMWH-calibrated anti-FXa assays can be used in emergency settings to reliably rule out clinically relevant concentrations of rivaroxaban and apixaban, though they are not suitable for precise quantitative determination.
Effect estimate: κ = 0.76 (95% CI 0.56-0.96)
INTRODUCTION: Clinical application of rivaroxaban and apixaban does not require therapeutic monitoring. Commercial anti-activated factor X (anti-FXa) inhibition methods for all anti-FXa drugs are based on the same principle, so there are attempts to evaluate potential clinical application of heparin-calibrated anti-FXa assay as an alternative method for direct FXa inhibitors. We aimed to evaluate relationship between anti-FXa methods calibrated with low molecular weight heparin (LMWH) and with drug specific calibrators, and to determine whether commercial LMWH anti-FXa assay can be used to exclude the presence of clinically relevant concentrations of rivaroxaban and apixaban. MATERIALS AND METHODS: Low molecular weight heparin calibrated reagent (Siemens Healthineers, Marburg, Germany) was used for anti-FXa activity measurement. Innovance heparin (Siemens Healthineers, Marburg, Germany) calibrated with rivaroxaban and apixaban calibrators (Hyphen BioMed, Neuville-sur-Oise, France) was used for quantitative determination of FXa inhibitors. RESULTS: Analysis showed good agreement between LMWH calibrated and rivaroxaban calibrated activity (κ = 0.76) and very good agreement with apixaban calibrated anti-Xa activity (κ = 0.82), respectively. Low molecular weight heparin anti-FXa activity cut-off values of 0.05 IU/mL and 0.1 IU/mL are suitable for excluding the presence of clinically relevant concentrations (< 30 ng/mL) of rivaroxaban and apixaban, respectively. Concentrations above 300 ng/mL exceeded upper measurement range for LMWH anti-FXa assay and cannot be determined by this method. CONCLUSION: Low molecular weight heparin anti-FXa assay can be used in emergency clinical conditions for ruling out the presence of clinically relevant concentrations of rivaroxaban and apixaban. However, use of LMWH anti-FXa assay is not appropriate for their quantitative determination as an interchangeable method.
Margetić et al. (Fri,) conducted a cross-sectional in Non-valvular atrial fibrillation (n=61). LMWH-calibrated anti-FXa assay vs. Drug-specific calibrated anti-FXa assay was evaluated on Agreement between LMWH calibrated and rivaroxaban calibrated anti-FXa activities (κ = 0.76, 95% CI 0.56-0.96). LMWH-calibrated anti-FXa assays showed good agreement with drug-specific assays (κ = 0.76 for rivaroxaban, κ = 0.82 for apixaban) and can reliably exclude clinically relevant concentrations of these drugs.